Layout, Packaging, and Efficiency Implications of a 1.7 kV Hybrid Si/SiC Reverse Blocking Switch Module in Soft-Switching Current Source Converters

Abstract

The Soft-Switching Solid-State Transformer (S4T) is a flexible, multi-port, and isolated ZVS soft-switching power converter with emerging applications in multi-port data center power delivery, renewable energy integration in EV fast charging stations, and storage integration in next generation solar farms. As a current source converter, the S4T requires reverse blocking (RB) semiconductor devices with bidirectional voltage blocking capability and unidirectional current flow. While these switches had been implemented from the series connection of discrete devices in early S4T prototypes, larger scale projects require a more manufacturable, cost-effective, robust, and compact approach. This work presents the first device-level analysis of the soft-switching principles of the S4T in a commercial, high current 1.7 kV RB switch phase-leg module in which each switch position consists of the series connection of a Si IGBT and a SiC Schottky diode. The hybrid RB module was extensively tested in a soft-switching current source inverter bridge, replicating the unique ZVS soft-switching environment of the S4T, and enabling measurement of conduction loss, residual switching loss, and dI/dt and dV/dt stress. With Si IGBTs, residual switching loss from IGBT tail current and commutation loop parasitic inductance limited the achievable turn-off energy reduction under soft-switching. Nevertheless, the ZVS soft-switching environment of the S4T enabled a > 88.8% reduction in turn-on loss and a > 55.2% reduction in turn-off loss at 800 V and 90°c cold plate temperature.